alcohols, thiols, phenols, and ethers
TRANSCRIPT
ALCOHOLS, THIOLS, PHENOLS, AND ETHERS
by Marvin B. Gonzaga
ALCOHOLS• contain a hydroxyl group (OH)
attached to an alkyl group • the hydroxyl groups of alcohols
are very polar because of the significant difference between the electronegativities of the oxygen and hydrogen atoms.
Ethanol
• because of intermolecular hydrogen bonding, alcohols boil at much higher temperatures than hydrocarbons of similar molecular weight.
CH3CH2CH2CH3ButaneM.W. = 58
b.p. = -0.5 ℃
CH3CH2CH2OH
1-PropanolM.W. = 60
b.p. = 97.2 ℃
• Alcohols of 1 to 4 carbon atoms are very soluble in water.
• Those with 5 to 6 carbons are moderately soluble in water.
• As the nonpolar, or hydrophobic portion of an alcohol (the C chain) becomes larger relative to the polar, or hydrophobic region (the hydroxyl group), the water solubility of alcohol decreases.
ALCOHOLS
Alcohols of 7 or more C
atoms are nearly insoluble in water.
PHENOLS
• Compounds in which the hydroxyl group is attached to a benzene ring.
• They are polar compounds and are somewhat soluble in water.
• They are found in flavorings and fragrances and are used as preservatives
Mint
PHENOLS
Thymol
PHENOLS
Oregano
Carvacrol
ETHERS
• have the general formula R—O—R• The C—O bonds of ethers are polar.• Do not form hydrogen bonds to one
another because there is no –OH group.• They have much lower boiling points
than alcohols of similar molecular weight but higher boiling points than alkanes of similar molecular weight.
ETHERS
• Diethyl ether was the first general anesthetic used.
• Halogenated ethers are also used as general anesthetics and are less flammable than diethyl ether
Diethyl ether
THIOLS
• Compounds that contain the sulfhydryl group (—SH)
• Similar to alcohols in structure, but oxygen is replaced by sulphur.
• Thiols and many other sulphur compounds have nauseating aromas.
Skunk
Geraniol